The present invention relates to an elevator hoist apparatus, and in particular to a hoist apparatus disposed in a machine room at the bottom of an elevator hoistway which has an improved means for securing the hoist apparatus to the wall of the hoistway as well as an improved hoist drum.
FIG. 1 illustrates a conventional elevator apparatus of the type in which a hoist apparatus is disposed in an machine room near the bottom of an elevator hoistway. In the illustration, an elevator hoistway 1 has a machine room 2 provided at its lower end just above the pit 1a of the hoistway 1. In the machine room 2, a hoistway apparatus is provided which comprises a hoist 4, a base 3 on which the hoist 4 is mounted and which is secured to the floor 2a of the machine room 2, and means, comprising elements number 8 through 11, for rigidly attaching the end of the base 3 to the wall of the pit 1a just below the machine room 2. The hoist 4 comprises an unillustrated motor, an unillustrated reduction gear driven by the motor, and a hoist drum 4a which is mounted on the output shaft of the reduction gear. The hoist drum 4a has a plurality of main ropes 7 wrapped around it which pass over a deflector sheave 6 disposed in the top of the elevator hoistway 1 and connect to the frame 5a of an elevator car 5 which is suspended from the main ropes 7 and which travels up and down the hoistway 1.
As shown most clearly in FIG. 3, the base 3 comprises a plurality of horizontal beams 3a which are secured to the floor 2a of the machine room 2 by suitable unillustrated means such as anchor bolts and which each have one end secured to the wall of the hoistway 1 by the above-mentioned attaching means comprising elements numbers 8 through 11. Element number 8 is a metal securing plate which is bolted to the wall of pit 1a by fixtures 9 comprising nuts and anchor bolts or the like. The top end 8a of the securing plate 8 is bent outwards into the elevator hoistway 1 and is secured to the base 3 by fixtures 11 comprising nuts and bolts or the like which pass through holes formed in the beams 3a and corresponding holes formed in the top ends 8a of the securing plate 8. Elements number 10 are metal connecting plates which have their bottom ends secured to the sides of the securing plate 8 by welding and which have their upper ends secured to the ends of the base 3 by fixtures 11 comprising nuts and bolts or the like. Thus, the base 3 on which the hoist 4 is mounted is secured to the securing plate 8 which in turn is secured to the wall of the pit 1a of the hoistway 1 just below the machine room 2.
This means for securing the hoist 3 to the wall of the pit 1a of the hoistway 1 has the following disadvantages. First of all, because the top ends of the connecting plates 10 are secured to the ends of the base by bolts, the ends of the base 3 must protrude into the hoistway by a length A in order to provide sufficient strength and to provide enough space for the manipulation of tools when installing the bolts. In this hoist apparatus, the length A can not be significantly reduced, and it is thus difficult to install a hoist apparatus of this type in a narrow hoistway. Another problem is the large number of fixtures which are necessary to connect the base 3 to the securing plate 8. Furthermore, as shown in FIG. 3, the width A.sub.1 of the base 3 must just equal the width of the securing plate 8, and the distance A.sub.2 between the holes formed in the top ends 8a of the securing plate 8 must just equal the distance between the corresponding holes for the fixtures 11 formed in the beams 3a in order for the securing plate 8 and the beams 3a to be properly connected to one another. The manufacture of the base 3 and the plate 8 therefore requires considerable precision and the connection of the base 3 to the securing plate 8 is difficult.
A more serious problem relates to the use of a single large securing plate 8 for securing the base 3 to the wall of the pit 1a of the hoistway 1. This problem is illustrated in FIG. 4, which is a view of the hoist apparatus of FIG. 3 taken along Line II--II. The wall of the pit 1a of the hoistway 1 is generally made of concrete, and in most cases is not perfectly smooth. A wide securing plate 8 which spans the entire width of the base 3 can therefore not lie flat against the wall of the pit 1a but will be supported by only a few locations with the other portions of the securing plate 8 being separated from the wall of the pit 1a. In order to rigidly secure the securing plate 8 to the wall of the pit 1a in this case, it is necessary for the anchor bolts of the fixtures 9 to be much tighter than if the entire securing plate 8 were able to lie flat against the wall. The securing plate 8 will be bent by the tightening of the anchor bolts, and the resistance to bending of the securing plate 8 will tend to pull the anchor bolts out of the wall. Thus, from the standpoint of structural strength, this means for securing the base 3 to the wall of the pit 1a is undesirable and potentially dangerous, as the bolts of the fixtures 9 may be torn out of the wall of the pit 1a by the forces acting on them.
Another problem with this conventional type of elevator will be explained with reference to FIGS. 5-7. FIG. 5 is a front vertical view of the conventional elevator apparatus of FIG. 1, showing in more detail the drum 4a of the hoist 4. As can be seen, the drum 4a has two sets of spiral rope grooves 4b and 4c formed therein which spiral from opposite ends of the drum 4a towards the center. A first set of rope grooves 4b has a first main rope 7a wound around it, and a second set of rope grooves 4c has a second main rope 7b wound around it. Both main ropes 7a and 7b pass over the previously-mentioned deflector sheave 6 and connect to the frame 5a of the elevator car 5. Elements number 12 are the landings of the building in which the hoistway 1 is provided.
As shown in FIG. 6, which is a top view of the elevator hoistway 1 taken along Line III--III of FIG. 5, due to lack of space, the deflector sheave 6 is generally not located directly above the lengthwise center of the drum 4a but is displaced towards one longitudinal end of the drum 4a. Accordingly, the angles between the longitudinal axis of the drum 4a and each of the main ropes 7a and 7b are not equal. This is illustrated in FIG. 7, which is a schematic view showing the geometrical relationship between the drum 4a and the deflector sheave 6 of the elevator of FIG. 5. In the figure, L.sub.0 is the distance between the axis of the sheave 6 and the top surface of the drum 4a, theta 1 is the angle between the top surface of the drum 4a and the first main rope 7a, and theta 2 is the angle between the top surface of the drum 4a and the second main rope 7b. Since the sheave 6 is not centered above the drum 4a, the angles theta 1 and theta 2 are not equal to one another. Accordingly, the distances measured along the main ropes 7a and 7b between the sheave 6 and the drum 4a, which are L.sub.0 /sin(theta 1) and L.sub.0 /sin(theta 2), respectively, are not equal to one another. Thus, as the lengths are not equal, the tension applied to the two main ropes will be unbalanced, causing an overloading of the first main rope 7a with respect to the second main rope 7b or vice versa, depending on the locations of the ropes along the drum 4a. This unbalance in the main ropes will shorten their lifespan, requires the use of larger main ropes than if both main ropes carried the same load, and may even result in the breakage of the main ropes.
Another problem with this type of conventional hoist apparatus is related to the means for securing the main ropes to the drum. This problem is illustrated in FIGS. 8 through 10. FIG. 8 is a front view of one lengthwise end portion of the drum 4a of a hoist like the one illustrated in FIG. 5, FIG. 9 is a partial cross-sectional view of the same drum 4a taken along Line IV--IV of FIG. 8, and FIG. 10 is a view of the drum 4a taken along Line V--V of FIG. 9. As shown in the figures, the main rope 7a has a cylindrical stopper 14 rigidly secured to its end. The stopper 14 fits into a hole 4g formed in the wall of the drum 4a. The hole 4g connects to a groove 15 of a rope guide 15 also formed in the wall of the drum 4a, the width of the groove 15a being slightly larger than the diameter of the main rope 7a but smaller than the diameter of the stopper 14. When the stopper 14 is inserted all the way into the hole 4g, the end of the main rope 7a contacts the inner surface of the groove 15a, and when tension is applied to the rope 7a, the top surface of the stopper 14 is forced firmly against the bottom surface of the rope guide 15. The other main rope 7b is connected to the drum 4a in a similar manner.
There is no problem with this manner of connection when the main ropes 7a and 7b are tautly wound around the drum 4a. However, if the elevator car 5 should reach the end of its travel and contact the unillustrated buffers generally provided in the pit 1a of the elevator hoistway 1, the main ropes will become slack and there will be no force preventing the stopper 14 from coming out of the hole 4g in the drum 4a. Accordingly, before the elevator car 5 can be allowed to again travel up the hoistway 1, it is necessary to check whether the stopper 14 is in fact securely held inside the drum 4a. This means for securing the ends of the main ropes is therefore is disadvantageous from the standpoint of safety.
As explained above, there is therefore a need for an improved elevator hoist apparatus which is better secured to the hoistway in which it is installed and which has a safer drum.